1. Field of the Invention
The present invention relates to an electric/electronic circuit preferably applicable to an integrated circuit device such as LSI (Large Scale Integrated Circuit) and capable of effectively preventing conversion of hardware in electric/electronic products, unlawful alteration or secondary use of software products or the like.
2. Description of the Related Art
In view of the foolproof and failsafe characteristics of electric/electronic products, conversion of hardware in electric/electronic products, alteration of software and the like are desirably rendered impossible on the user side.
Therefore, according to conventional techniques, special screws are employed for product cases, or software-wise countermeasure is provided in order to prevent conversion of such hardware in electric/electronic products or alteration or secondary use of software.
These devises could be effective to a certain extent for preventing conversion of hardware in electric/electronic products or alteration or secondary use of software, but the effect is not sufficient.
The present invention is directed to a solution to this problem, and it is an object of the present invention to provide an electric/electronic circuit device which can physically prevent conversion of hardware in an electric/electronic product and alteration, secondary use or the like of software with a simple structure.
It is another object of the invention to provide an electric/electronic circuit device which can prevent secondary use in the field once the user has used the product.
In the electric/electronic circuit device according to the present invention, the logical output of a logical output setting circuit is irreversibly fixed to a prescribed logical output based on a voltage applied to a particular terminal.
The use of the fixed logical output of the logical output setting circuit permits the operation of a logical element connected to the output side of the logical output setting circuit to be fixed.
Herein, the logical output setting circuit may have a (circuit) breaking element to be irreversibly disconnected based on a voltage applied on a particular terminal.
In this case, a boosting circuit is provided between the particular terminal and the breaking element so that the breaking element can be easily disconnected by the output of the boosting circuit if a voltage applied to the particular terminal is relatively low.
It is desirable that the boosting circuit is driven by a power-on reset circuit to set the boosting circuit to an operation state for a prescribed time period after a voltage is applied to the particular terminal, since the power consumption by the boosting circuit can be limited to a prescribed period.
If the boosting circuit is connected with a power consumption limiting circuit to reduce or eliminate the power consumption by the boosting circuit in response to detection of the disconnection of the breaking element, the power consumption by the electric/electronic circuit device can be reduced after the breaking element is disconnected.
The breaking element is disconnected by the output of the boosting circuit set to an operation state for a prescribed time period by the power-on reset circuit after a voltage is applied to the particular terminal. The boosting circuit is connected with a power consumption limiting circuit which reduces or eliminates the power consumption by the boosting circuit in response to detection of the disconnection of the breaking element, so that the power consumption by the boosting circuit can be reduced or eliminated in a normal state after the breaking element is disconnected.
When the electric/electronic circuit device is formed by an integrated circuit, the breaking element can be integrally formed by a silicon interconnection pattern.
If the particular terminal is a power supply input terminal for the electric/electronic circuit device and the user uses the electric/electronic circuit device for the first time, the logical output of the logical output setting circuit will be fixed.
An electric/electronic circuit device according to the present invention includes a logical output setting circuit having a logical output irreversibly fixed to a prescribed logical output when a voltage is applied to a particular external terminal and an electrically writable and erasable storage device connected to the output side of the logical output setting circuit.
According to the present invention, by the logical output of the logical output setting circuit, the operation of the electrically writable and erasable storage device can be defined.
More specifically, an external terminal for reading/writing control is connected to the reading/writing control input of the storage device, and reading/writing from/to the storage device can be controlled by using the external terminal for reading/writing control before a voltage is applied to the particular external terminal. As a result, the device can be used such that writing/erasure to the storage device can be performed as desired before the logical output setting circuit is fixed to a prescribed logical output, while after it is fixed to a prescribed logical output, writing/erasure is disabled.
Alternatively, the reading/writing control input of the storage device may be connected with an internal terminal for reading/writing control, and reading/writing from/to the storage device can be controlled by using the internal terminal for reading/writing control before a voltage is applied to the particular external terminal. As a result, for example reuse (writing/erasure) can be executed as many times as necessary on the side of the manufacturer of the electric/electronic circuit device.
More specifically, when a voltage is actually applied to a particular external terminal, the storage device can be used only as a read only memory by a fixed prescribed logical output of the logical output setting circuit.
The logical output setting circuit includes a breaking element to be irreversibly disconnected based on a voltage applied to the particular external terminal.
Also in this case, a boosting circuit is provided between the particular external terminal and the breaking terminal, so that the breaking element can be easily disconnected by a relatively high voltage output of the boosting circuit even if the voltage applied to the particular external terminal is relatively low.
It is desirable that the boosting circuit is driven by a power-on reset circuit to set the boosting circuit to an operation state for a prescribed time period after a voltage is applied to the particular external terminal, since the power consumption by the boosting circuit can be limited to the prescribed time period.
If the boosting circuit is connected with a power consumption limiting circuit to reduce or eliminate the power consumption by the boosting circuit in response to detection of the disconnection of the breaking element, the power consumption by the electric/electronic circuit device can be reduced after the breaking element is disconnected.
The breaking element is disconnected by the output of the boosting circuit set to an operation state by the power-on reset circuit for a prescribed time period after a voltage is applied to the particular external terminal, and the boosting circuit is connected with a power consumption limiting circuit to reduce or eliminate the power consumption by the boosting circuit in response to detection of the disconnection of the breaking element, so that the power consumption by the boosting circuit can be reduced or eliminated in a normal state after the breaking element is disconnected.
If the electric/electronic circuit device is formed by an integrated circuit, the breaking element can be formed by a silicon interconnection pattern.
The particular external terminal may be a power supply input terminal for the electric/electronic circuit device, so that once the user has used the device, the logical output setting circuit has its logical state fixed and cannot be subjected to secondary use in the field.
Furthermore, the electric/electronic circuit device according to the present invention may be formed to irreversibly fix the logical output of the logical output setting circuit to a prescribed logical output by supplying a current rather than applying a voltage to the particular terminal.
Similarly, the electric/electronic circuit device according to the present invention may be formed to have a logical output setting circuit having a logical output irreversibly fixed to a prescribed logical output by supplying a current rather than applying a voltage to the particular external terminal and an electrically writable/erasable storage device connected to the output side of the logical output setting circuit.
The above and other objects, features and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which a preferred embodiment of the present invention is shown by way of illustrative example.